Yea you can shift into first anytime. Its kind if annoying when wheeling. I would like the programming to start in first when in mode so it would go from R to D1 and back with one push as those ratios are closer together. I have heard that when you select first in normal configuration(not mode), it will also lockup the center differential like when in mode, but I have found no info to support that claim And havn't confirmed it my self(yet
).
As General mentioned 2-7 are the normal sequence. Those are the 6 ratios delivered by the 3000 series core transmission X the fixed 1.2:1 transfer case gearing.
GR RATIO CLUTCH
1st 6.93:1 C3-C6
2nd 4.18:1 C1-C5
3rd 2.24:1 C1-C4 + LU
4th 1.69:1 C1-C3 + LU
5th 1.20:1 C1-C2 + LU
6th 0.90:1 C2-C3 + LU
7th 0.78:1 C2-C4 + LU
R —5.00:1 C3-C5
We get our low first gear from the C6 clutch located in the top of the transfer case, but it does its magic inside the core transmission. A planetary has 3 gears, sun, planets and ring. To get a ratio, you brake/lock one, you spin one and the output is on the 3rd. The transfer case allowed them to put a hollow shaft on the transmission output to the top gear in the transfer case. On the normal 3060 transmission, the driveshaft yoke would have gone there.
Thru that hollow shaft they ran another shaft that allows that C6 clutch to brake the sun gear buried in the middle of the last planetary set, allowing an additional ratio out of the main gearbox.